A while ago my mom had a dream about where she was driving down her road and went around a curb. There was a small beach there and a bunch of dead people were just lying there. A person with an unknown gender umong them. She wouldn't tell me anymore than that.

Dreams represent a bunch of things. They can either represent issues that your subconscious is trying to warn you about or surface. Or they can just be simply so: dreams. Things that your mind make up just for the sake of making up.

I once dreamed that I was trying to shoot a gun for practice, but it turned into a banana.

This sounds like something your mom might be facing. The bodies on shore might represent past issues that are currently being "washed up".

It could be the other thing. Her mind might be making up things for the sake of making up things.